X-ray CT apparatus

Abstract

An X-ray CT apparatus is configured capable of properly calculating a radiation dosed amount more approximating to an actually exposed radiation dose that includes scattering rays of an examined object from data measured at the scanning time. A function or table showing a relationship between data obtained on the basis of the measured data of the object detected by an X-ray detector at the scanning time and the radiation dosed amount is stored in advance; and the X-ray CT apparatus calculates the radiation dosed amount of the object in accordance with the data obtained on the function or table showing the relationship between the data obtained on the basis of the measured data of the object stored in advance and the radiation dosed amount.

The invention claimed is: 
     
       1. An X-ray CT apparatus comprising:
 an X-ray source configured to irradiate X-rays to an object to be examined; 
 an X-ray detector disposed facing the X-ray source, and configured to detect the X-rays transmitted through the object; 
 a scanner in which the X-ray source and the X-ray detector are mounted, configured to rotate them around the object, for a plurality of views; 
 an image reconstruction device configured to reconstruct a tomographic image of the object based on a dose of the transmitted X-rays detected by the X-ray detector; 
 image display device configured to display the tomographic image reconstructed by the image reconstruction device; 
 a storage device that stores a mathematical function, or a table, representing a relationship between (a) a first value equivalent to cross-sectional area of a phantom calculated based on measured data of the phantom detected by the X-ray detector and (b) a second value corresponding to radiation dose absorbed in the phantom including scattered X-rays; and 
 a radiation dose calculating device configured
 to calculate radiation dose absorbed in the object in a view, by inputting to the mathematical function a value equivalent to cross-sectional area of the object calculated based on measured data of the object detected by the X-ray detector upon tomographic image scanning, or by comparing the value equivalent to the cross-sectional area of the object with first values in the table, and 
 to calculate actual radiation dose absorbed in the object upon tomographic image scanning by using summation of the radiation dose calculated or determined for each view amongst the plurality of views. 
 
 
     
     
       2. The X-ray CT apparatus according to  claim 1 , wherein the function or the table expresses the relationship between projection data obtained by correcting measured data of the phantom and radiation dose including scattered X-rays. 
     
     
       3. The X-ray CT apparatus according to  claim 1 , wherein the function or the table expresses the relationship between difference data of measured data of the phantom and those without the phantom and radiation dose including scattered X-rays. 
     
     
       4. The X-ray CT apparatus according to  claim 1 , wherein the function or the table is created in advance based on the data obtained by measuring a plurality of phantoms having different sizes according to IEC standard. 
     
     
       5. The X-ray CT apparatus according to  claim 1 , wherein the display device displays the radiation dose calculated by the radiation dose calculating device and the radiation dose prescribed by a predetermined standard along with the tomographic image.